Recently, discussions on an advanced long term evolution (LTE) communication system (LTE-A), in which various new technologies are grafted into the LTE communication system to increase a transmission rate, have been progressed in earnest. A representative of the newly introduced technologies for LTE-A may be carrier aggregation. The carrier aggregation uses a plurality of forward carriers and a plurality of backward carriers by one terminal unlike the conventional data transmission/reception using only one forward carrier and one backward carrier by the terminal
The current LTE-A defines only intra-ENB (Evolved NodeB) carrier aggregation. However, in order to guarantee a high data transmission rate of the terminal, a necessity of a technology for aggregating different cells in an environment in which a plurality of cells having different sizes operate while overlapping each other is currently generated. Accordingly, currently, in 3GPP Rel-12, inter-ENB carrier aggregation or a technology of dual connectivity between different types of ENBs that combines and uses serving cells belonging to different ENBs is being discussed. For example, in 3GPP Rel-12, performance of dual connectivity by which each terminal is simultaneously connected to two different ENBs is being discussed. However, a detailed method of transmitting and receiving data of the terminal in a dual connectivity state has not been yet proposed, so that it is required to provide a detailed method of data transmission and reception of the terminal.